I my name is Dee, I am new to this forum but needs some serious advice on my issues with my idle, I have very little experience with cars but do have enough common sense to handle a small task.

RE: 1994 Toyota 4 runner V6 3.0, miles 244k,

Car drives fine after a while of driving when it's idling engine will hesitate then idle gets rougher, Then eventually it will shut itself off. I have change the spark plugs, wires, distributor cap, rotor, fix a leak in vacuum hose, replace fuel filter. It shows a little improvement it still idles rough and shut itself off. spark plugs gap is correct, cylinder fire order is correct, Seems like all vacuum hose is in tact. Is there something else I am missing here, I have heard of EGR valve not really sure what that does, Ignition coil etc. Is there something else that I should replace. I see on the on top of cylinder block there is a loose wire plug, is that suppose to plug into something. I have a picture of it where the arrow points!!

Yes, it does start back up but I have to gas it for it to stay on, if i let go it will shut off. If the engine cools off for a while it idles fine for a short time.,the wires is not connected to a harness, looks like it suppose to connect to something. You know anything about idle or ignition timing.

Yes the engine light is on, the connector is black , looks like a copper male connector, is it suppose to ground to something. I have a attach a better picture. I have not check the air flow meter as of yet! how do I check that?

Ok...that connector is an engine ground. The other half of the connector should be coming off the firewall.

Since the check engine light is on, there are code(s) stored in the ECU. To retrieve the codes you need to find the diagnostic connector under the hood. Flip the cap open and there is a label that corresponds to the terminals in the connector. You want to take a piece of wire or paper clip and jump TE1 to E1. Turn on the ignition and the check engine light will flash the codes. Write down the numbers and let us know.

There is a rubber engine air inlet ducting that connects from the throttle body on the engine to the air flow meter on the air cleaner box. Make sure that ducting isn't ripped, damaged, or loose on the ends.

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

Hi, I did check the duct where you pointed out it seems fine, no rips or sign of damage unless there like a pinhole size I would not know how to point that out. Anyways I did check out the error code it came up 25 and 71. I hope that helps on pointing out where I need to be looking at. Thanks again for your help !

Dee S

P.S I am using NGK BKR5EYA spark plugs if that makes a difference in performance.. Thank You for your help!

Code 71 means the ECU detected an EGR problem. There is sensor that monitors the EGR gas temperature. When the EGR is opened by the ECU the temperature sensor sees a rise in exhaust gas temperature. If the ECU doesn't see this, it thinks there is a problem with the EGR not opening. This shouldn't cause your problem unless the EGR was staying open at idle.

Code 25 means the ECU is seeing a lean fuel condition. There is an O2 sensor in the exhaust that monitors the oxygen content in the exhaust stream. If the sensor sees high oxygen levels in the exhaust for a period of time, the ECU thinks the engine is running lean. This could cause the engine to stall because things that cause a lean condition are fuel related. You need to think of things that will cause an engine to run lean.

*Low fuel pressure * vacuum leaks *lower than normal voltage signal from the vane air flow meter for the actual air going into the engine. *injector flow problem *misfire causing the O2 sensor to sense high oxygen content *exhaust leak before the O2 sensor *stuck lean O2 sensor (this could cause the ECU to add more fuel to the engine making it run rich in close loop)

At the diagnostic connector you can actually monitor O2 sensor voltage using a digital volt meter. Plug the red lead of your meter into the Ox terminal and ground the meter to the negative post of the battery. When the O2 sensor is warmed up and operational it should be fluctuating between 0-1 volt. If it is less than .5 volt, that means it is seeing a lean condition. If it is over .5 volts that means it is seeing a rich condition. It fluctuates between those voltages which is normal. If it stays at below .5 volt and never goes higher than that, the engine is running lean.

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

I don't even know where to begin? I do appreciate you finding out what what I need to tackle to get this resolve. I have been reading up on the EGR system , before I bypass the EGR system I would like to test the valve to see if it is functioning properly. Do you know how I can test to see if it it functioning properly. What test procedure should I take to test it out, would taking in out and inspecting it would that be easier I know that carbon tends to build up in there. You said if the EGR valve opens when idling that may cause the rough idling. How do I check if it is open?

Code 25 is a long list: I am no mechanic and I do not have enough experience to trouble shoot this probabilities. Vacuum leaks I can try to check out every hose, low fuel pressure ? how do I check that. Air flow going to the engine? Misfiring would that have to do with sparks plugs, wires, cap, rotor.? injector flow problem, I did change the fuel filter, but not the pump. Exhaust leak? Stuck lean 02 sensor, is this the computer system telling my car to behave this way?

I do appreciate your help. I will try a few more troubleshooting ? If I do not get it fix soon I may have to sell it or take it to a mechanic which I would hate to do with the the financial situation I am in. Do you have any suggestion how much this would cost me or shall I just dump this car.